As Eric Fields and Daniel Szuc point out in their comments, the best partners not only get it, but can add great value as a result. My experience has been that some clients — for whatever reason — sometimes fail to understand their own businesses well enough to work effectively with their web partners. Perhaps they just can’t see the forest for the trees, or maybe they’ve never needed to dig deep before. But as a friend and colleague once told a clueless internal customer, “You need to understand, the website can’t miraculously solve your business problem; it can, however, magnify your dysfunction.”

If you’ve got the right skillset at the table, the site or application design process can (and should) expose business processes to the light of day, driving improvement, promoting efficiency and revealing new opportunities. And what could be better for business than that?

Just as its important to validate design decisions about what you know about the customer, it can be just as refreshing to revisit assumptions the business is making about their own business.

Unfortunately, discussions sometimes turn into “design by committee” and the framework of business and customer discussions disappear quickly.

As a designer, I love talking through the business application of landing page X or feature Y. I’ve encountered moments where a half hour of explaining and question asking has gone back and forth and suddenly there’s an air of confusion in the room, and I’m not always the confused one. You sometimes help a client find a small hole or two in their model, so you talk out how it might be able to be fixed this way or that way. There’s a chance that at the end of the meeting, I’ve helped him figure out a missing link of sorts. Now I know I’ve got a client for life.

To know the business is to know the design. When the client knows you know the business, then he or she will have total confidence in your work.